1. Field of the Invention
In general, the present invention relates to inflatable liners that are used between a partially amputated limb and a limb prosthesis. More, particularly, the present invention relates to the structure of a liner, its inflation mechanisms and its interaction with both the amputated limb and the limb prosthesis.
2. Prior Art Description
Many people who have amputated limbs or partially amputated limbs rely upon prosthetics to live more active lives. When a person is fitted for a limb prosthesis, that person may be fitted with a limb liner. A limb liner is typically worn over the portion of the limb that remains on the body. A limb liner is an elastomeric device that is pulled over the residual limb. The liner conforms to the shape of the residual limb and creates a strong frictional attachment to the skin of the residual limb. In many instances, a metal locking pin extends from the tip of the limb liner. The locking pin is used to engage the prosthetic limb when a prosthetic limb is mated with the limb liner. As such, the limb liner acts as the anchor for retaining the limb prosthesis onto the residual limb.
When a limb prosthesis is manufactured, a cast is taken of the limb liner while the limb liner is being worn. The cast is used to produce a socket. The socket is then attached to the limb prosthesis. The socket of the limb prosthesis is the portion of the prosthesis that mates with the limb liner and conforms to the shape of the limb liner and the underlying residual limb. In this manner, the limb prosthesis will properly fit onto the limb liner and residual limb.
Amputees commonly retain their prosthetic limbs for many years. However, during this time, the amputee may gain weight, lose weight, lose muscle mass, or otherwise undergo physiological changes. Furthermore, amputees may retain water, have limb swelling or undergo other physical changes that can cause the size of the amputated residual limb to vary. As the residual limb changes in size and/or contour, the configuration of the limb liner also changes. As a result, the shape of the limb liner may no longer match the shape of the socket in the prosthetic limb. This mismatch in shape creates gaps between the limb liner and the socket of the prosthesis. The gaps can cause the prosthesis to feel loose in certain places and overly tight in others. Furthermore, the gaps can cause physical discomfort by causing chafing against the residual limb.
In the prior art, fabric-based liner socks have been used to compensate for any inconsistencies between the configuration of the limb liner and the configuration of the limb prosthesis. Prior art liner socks are basically knitted or woven socks that are worn over the limb liner. The liner sock becomes compressed at points of contact between the limb liner and the limb prosthesis. The liner sock is less compressed in areas of gaps. Accordingly, the liner sock helps to fill the gaps between the limb liner and the prosthesis.
The ability of a knitted or woven sock to fill a gap is limited to gaps that are typically less than 1/32nd of an inch wide. In situations where larger gaps are commonplace, amputees typically turn to a gel liner or multiple layers of knitted socks. Gel liners are socks molded from an elastomeric material. These gel liners are worn around the limb liner when the limb liner is inserted into the socket of the prosthesis. The problem associated with such gel liners is one of compromise. The socket of the prosthesis is created from a mold of the limb liner. Accordingly, these two elements tend to be very close in shape. If the amputee's residual limb undergoes some physiological change, then that change may be localized. That is, only certain segments of the amputee's residual limb change, while the majority remains relatively the same. When a gel liner or multiple socks are used, the padding adds thickness to the entire limb liner. Accordingly, the segments of the limb liner that fit properly are now tight. In many situations, the discomfort created by a gel liner outweighs its benefits. Accordingly, gel liners are made thin, but not too thin so as not to be able to fill a gap. This compromise often makes gel liners either too loose or too tight, or both in separate areas.
The disadvantages of a gel liner can be avoided by the use of an inflatable liner. In the prior art, several inflatable liners have been invented for use between amputated limbs and prostheses. The inflatable liners can be selectively inflated to provide an adjustable interface between the residual limb and the prosthesis. However, prior art inflatable liners typically embody at least one of two major disadvantages. The disadvantages are either that the bladder is built into the socket of the prosthesis or that the bladder is used in place of a traditional limb liner.
In both U.S. Patent App. Pub. 2003/0078674, to Phillips, entitled Socket Insert Having A Bladder System, and U.S. Patent App. Pub. 2003/0181990, to Phillips, entitled Socket Insert Having A Bladder System, an inflatable bladder system is shown where the inflatable bladder is formed as part of the prosthetic's socket. These references provide bladders in only some parts of the socket. Accordingly, there is no guarantee that the bladders will fill any gaps that may exist between the amputee's limb and the sock. Furthermore, the bladder system is built into the structure of the prosthetic socket. The socket is custom made for each amputee and is both expensive and time consuming to manufacture. Adding bladders to this structure significantly increases the cost and labor of manufacture, thereby making this expensive component more expensive while significantly decreasing the reliability and life expectancy of the socket.
In U.S. Pat. No. 5,156,629 to Shane, entitled Pneumatic Prosthetic Insert, and U.S. Pat. No. 5,387,245 to Fay, entitled Inflatable Prosthetic Liners, inflatable limb liners are disclosed. These inflatable limb liners are designed to take the place of the elastomeric limb liner around which the socket of the prosthesis is molded. By eliminating the elastomeric limb liner, room is made for the inflatable limb liner.
As will be understood among amputees, residual limbs vary widely in shape and contour from patient to patient. This is why the socket of a prosthesis is custom molded to a limb liner. By replacing the limb liner with a single-sized inflatable liner, it would be impossible to create a quality interconnection between the residual limb and prosthetic socket of most amputees. Furthermore, inflatable limb liners lack the physical structure to support a connector pin. The connector pin creates the strongest mechanical interconnection between the limb liner and the prosthetic limb. Without a connector pin, many amputees would not be able to keep the prosthetic limb attached to their bodies during normal everyday activities.
A need therefore exists for a new type of inflatable interface that is designed to lay between an ordinary prosthetic limb socket and an ordinary limb liner having a connector pin. A need also exists for an inflatable interface that is very thin so as not to make the limb liner feel tight in well-fitted areas. However, the inflatable interface can be selectively inflated to fill significant gaps that may be encountered between the limb liner and the prosthetic limb socket. Lastly, a need exists for an inflatable interface where the limb liner has no adverse effect upon the ability of the limb liner pin to interconnect with the limb prosthesis. These needs are all met by the present invention as described and claimed below.